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Figure 2.2-3. Display preferences.
2.2.4. Data Filters tab
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Figure 2.2-4. Three data filtering options on the Data Filter tab: Decimate, Gaussian Smoothing, and Cull. Shown is a 9-point Gaussian filter applied to the magnetic susceptibility data whereby both original and smoothed (white trace overlay) are plotted. The filter can be edited or deleted.
2.3. Application menus
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2.3.1. File menu
Figure 2.3-1. File menu.
2.3.2. Edit menu
Figure 2.3-2. Edit menu.
2.3.3. View menu
The View menu has a few fundamental display preferences not available in the Display Preferences tab of the Display view (Fig. 2.3.3-1.)
Figure 2.3-3. View menu.
3. Manage data in Correlator
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Figure 3.6-2. Export options. A. Export all raw data for this data type. B. Export all data with CCSF depth column added for this data type. C. Export the splice for this data type.
Export spliced data and images
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4. Depth shift cores
4.1. Depth shift concepts
Affine constraint
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4.2. Shift cores with the TIE method
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4.3. Shift cores with the SET method
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4.4. Undo shifts
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4.5. Manage affine tables
The goal of depth shifting is to construct a composite depth below seafloor (CCSF) depth scale by arranging the cores from one or more holes in a way that the combined data better represent the stratigraphy at a site than the cores do at their standard CSF-A depth scales.
The composite depth scale is defined in an affine table where each core has a cumulative offset, the difference between its CCSF and CSF-A depths. The affine constraint stipulates that no virtual stretching or squeezing is allowed within a core. This is a practical and effective approach because (A) it is based on straightforward rules and avoids the implementation complexity of virtual stretching and squeezing, and (B) sampling of the physical cores would become overly complicated if the CCSF depth scale was distorted in the correlation process relative to the CSF-A scale, which is true to the physical samples. Correlation under the affine constraint creates a “~95%” solution quickly and effectively, whereas resolving the remaining “~5%” of the correlation involves a lot more work and subjectivity and the result is far more difficult to apply.
The coring process does stretch and squeeze cores to a certain degree, and this artificial stratigraphic distortion, combined with actual variability in the stratigraphy in multiple holes, means that between two cores only one stratigraphic feature can be exactly correlated and assigned the same composite depth. Other correlative features will have somewhat different composite depths.
Shifting methods
Depth shifts can be defined by one of two methods: by creating a tie between two cores (TIE method) or by shifting a fixed amount or percentage of depth (SET method). A core shifted with the SET method can later be shifted by the TIE method, however, cores that are tied (part of a chain) cannot be shifted by the SET method. Cores have a type designation based on the (last) shift method applied: REL, TIE, or SET. These designations are used programmatically to implement the above rules and to control the color of the core data trace.
- At the beginning, all cores are of type REL (relative positions to each other based on the original CSF-A depth) and the core traces are yellow.
- When cores are tied to another core based on correlation features, their status changes to TIE and their traces are green.
- When cores in a single hole are shifted by a fixed offset or by a percentage of their CSF-A depth, the status of cores shifted in this manner changes to SET and trace turns orange.
- However, when an entire chain of tied cores, including cores from multiple holes, are shifted by a fixed amount, the cores’ status does not change, they are still TIE.
- If a core of status SET is tied, its status changes to TIE and the trace color turns green.
Correlator keeps track of the cumulative offset of each core resulting from all shifts applied, the method used for the latest shift, and in the case of TIE relationships, the core to which a given core was tied. The specification for the affine table was expanded with Correlator version 3 for the purpose of recording the latest shift method and the tie relationships (see Appendix 2 for the affine table specification).
Chaining cores
Coring in one hole can never recover a complete stratigraphic sequence. Ideally, two holes can achieve that if the cores in the second hole are offset sufficiently to cover the coring gaps in the first hole. A CCSF scale is then defined by tying cores from the top (as close to seafloor as possible) to the bottom (as deep as correlations are possible), establishing ties from reference (REF) cores to shifting (SHIFT) cores, thus creating a simple chain of cores.
In many if not most cases, cores from two holes cannot achieve complete stratigraphic coverage due to a number of factors and cores from a third or even fourth hole are needed. Since the goal is (should be) to tie all cores from all holes into the CCSF framework, the cores will not form a simple chain anymore, but include multiple chain branches. A new chain branch is created when a core serves as a REF core for two or more SHIFT cores. Under no circumstance can a core be a SHIFT core to more than one REF core due to the affine constraint.
Because the CCSF scale construction proceeds from top to bottom, “upstream” tie changes, i.e., changing the tie from a SHIFT core to its REF core, are simply forbidden. Upstream tie changes would have undesirable and unintended effects. In such cases, the user needs to decide where to implement the tie change further upstream so the tie break effect is directed downstream. Downstream directed tie changes preserve the ties unless a chain branch must be broken off, which the program can identify and the user can be prompted to accept the consequence or cancel the action. An example will be given below.
Summary of shift rules
- A core can be depth shifted once or multiple times, resulting in one single cumulative offset, which is the difference between its top depth at the constructed CCSF scale and that at the original CSF-A scale.
- Cores can be shifted by the TIE method or the SET method.
- Two cores can be related with only one tie due to core distortion, stratigraphic variations from one hole to the other, and the affine constraint.
- A core can be REF core to multiple SHIFT cores, however, a SHIFT core can only be shifted by one REF core.
- Cores related with TIEs form a chain. If a core is the REF core for more than one SHIFT core, chain branches are formed.
- Upstream tie changes are not allowed. Downstream tie changes are allowed and users will be prompted to accept resulting tie breaks or cancel the action.
4.2. Shift cores with the TIE method
Depth shift controls and feedback
The user can shift cores by establishing tie points for two cores on the basis of correlative features in the data or by opting for a statistical correlation.
• Note: these ties are only for the purpose of shifting cores. They are not “splice ties”. However, in anticipation of splicing, the best correlation between two cores may be chosen where a splice interval boundary is likely to be established because alignment of stratigraphic features in other parts of the cores is not guaranteed.
To shift cores, select the Shift Cores tab of the Display view to see the control pane (Fig. 3-21), which provides both the controls for shifting cores and the feedback on the progress of shifting.
• Note: you can shift cores without selecting the Shift Cores tab, operating strictly with the context menu. However, you won’t have all controls or the graphic feedback.
At the top of the Shift Cores control pane three plots are available to choose from:
• Evaluation: This is a correlation coefficient plot that can provide a statistical assessment of how well two cores correlate (Fig. 3-21A).
• Growth Rate: This is a plot of the composite depth (CCSF) vs. the original depth (CSF-A) for each core top. The slope of the core segments is the “growth rate” (Fig. 3-21B). For APC-XCB coring, the rate is typically between ~1.2 to 1.0, gradually decreasing downhole as the formation gets firmer and elastic and gas expansion upon recovery diminish. If the curve exhibits erratic changes in growth rate for a hole or a core, and unless an unusual stratigraphic phenomenon exists, something may be wrong with the correlation.
• Shifts: This is a convenience display of part of the new affine table, listing all cores in play (Fig. 3-21C).
¿ Core column: identity of hole and core.
¿ Shift column: current offsets applied in Correlator
¿ Type column: relationship a core has to other cores: TIE, REL and SET, as described above.
Beneath the graphic are the controls for depth shifting. The most important tie shift controls are also available as context menus.
Figure 3-21. (A) Shift Cores tab with Evaluation plot, (B) Growth Rate plot and (C) Shifts plot.
Basic procedure
Core traces are colored based on the depth scale and shift status of the cores. At the beginning, all core traces are yellow, indicating that they were not shifted and are still at the original CSF-A depth scale (Fig. 3-22). They have the status REL, meaning their positions are relative to the previous core as defined by the CSF-A scale. The fact that yellow traces and status REL go together is trivial at this stage but not later on.
Figure 3-22. Before any shifts are made, all core traces are yellow, all cores are of type REL, and all offsets are zero.
To prepare the first tie, we select the core with the shallowest data as the “anchor” or “root” core as the reference (REF) core. In the case of our example (Fig. 3-23), this is core B1:
• Shift-click the trace of REF core B1. A red dot and horizontal line will appear.
• Shift-click the trace of SHIFT core A1. A green square and horizontal line will appear.
• Furthermore, a white and red copy of the data trace from the SHIFT core is overlain on the trace of the REF core to visualize the correlation.
• Select the Evaluation graph on the control pane to show the best statistical correlation for the proposed shift.
• Make adjustment to the shift to achieve the desired correlation in one of two ways:
¿ Select “To best correlation” from the control pane (Fig. 3-24). This option does not have a context menu equivalent. The alternative is to shift “To tie”, the more common option. Note that using the statistical “To best correlation” option blindly may result in unexpected shifts!
¿ Arrow the green dot up or down to achieve the visually most appealing correlation on either the Evaluation graph or the trace overlay. This is perhaps the more common practice.
Figure 3-23. Preparing the first tie by shift-clicking the reference (REF) core B1 (red dot and horizontal line) and the SHIFT core A1 (green square and horizontal line).
Figure 3-24. Tie control options “To tie” and “To best correlation”.
• Next you can pick one of two shift scope options by either right-clicking the green dot or by using the widget on the control pane (Fig. 3-25):
¿ “This core and all related cores below” is the more commonly used option because it prevents shifted cores from “running over” un-shifted cores as you proceed deeper in the hole.
¿ “This core only”.
• Committing to or cancelling the shift works differently in the context menu and the control pane:
¿ In the context menu, selecting one of the two scopes in Fig. 3-25A executes the shift, and the “Clear tie point(s)” option cancels it.
¿ On the control pane, two buttons are available to Apply Shift or Clear Tie (Fig. 3-24).
Figure 3-25. The user can pick one of two scope options: “This core and all related cores below” or “This core only”. Shown are (A) the options on the context menu and (B) the options on the control pane.
A. B.
• Once you commit to the shift, the following happens (Fig. 3-26):
¿ A white arrow is drawn from the REF tie point to the SHIFT tie point, one arrow for each data type.
¿ The SHIFT core’s trace turns green and its type changes to TIE
¿ If “all related cores below” was selected, all core traces below the SHIFT core turn orange and their type changes to REL because they are still in the original relative position to each other.
¿ The shift table shows the offset amount of the SHIFT core (and all cores below, if that was the selection), and indicates the REF core used for the shift (B1 in Fig. 3-26 example).
¿ The growth rate plot is updated (plot examples are shown in Figs. 3-21 and 3-27).
Figure 3-26. First tie is completed.
The remaining controls on the Shift Cores tab (SET, Undo and Save) are described in subsequent sections.
Changing ties
What happens when you change your mind about a tie between two cores and want to redo it? Or what if you created a chain using cores from the first two holes, and now core data arrive from the third hole and it makes sense to “weave them in”? The latter scenario is exemplified by Fig. 3-26 where it is obvious that the first core gaps in the first two holes align exactly, meaning that correlation of the first two cores to subsequent cores is not possible using only Holes A and B. We are therefore introducing additional data from a third Hole D.
Ties can be revised anywhere in an existing chain as long as the change is made downstream, i.e., in the direction of the existing tie, or if a new core (e.g., from Hole D) is added as a SHIFT core anywhere in the chain. All ties from related cores below the SHIFT core remain intact if the user selects to shift “all related cores below”.
Two exceptions exist.
• If you are trying to reverse the shift direction of a tie, Correlator will throw the error in Fig 3-27 if you try. The reason is that reversing a shift would lead to a SHIFT core having two REF cores, which is not possible. Thus, one would create a chain reaction of tie breaks. If you really want to reverse that tie, first break the offending tie (see below) and then repair your chain as needed.
• If multiple chain branches exist, a common occurrence when cores from more than two holes are tied into a chain, tie change may cause a conflict. Correlator will warn the user of the ties to be broken while preserving unaffected ties. You can decide whether to proceed and then fix the damage to the chain, or cancel the tie change (Fig. 3-28).
Figure 3-27. Reversing a tie direction to a SHIFT core is forbidden. In this case, a tie revision is attempted from B2>D2 (red and green dots). However, the existing tie B2>D2 tie does not allow that. The user would have to break that tie first.
Figure 3-28. A typical situation where applying a tie change creates a conflict. The user decided to correlate D2>A2 (see red and green dots). This is a “downstream” change and thus allowed. However, because D2>B2 and B2>A2 ties already placed D2 and A2 in a fixed relationship, the B2>A2 tie has to be broken if D2>A2 is to be tied.
Breaking individual ties
It may happen that you want to (or have to) break out a core from the chain because you found better chaining options. The easiest thing may be to delete a tie or two and correlate them again using suitable correlative features. This is now easy:
• Right click on a tie and selecting Break tie.
Alternatively, you can break a tie via the control pane:
• Go to the Shift table in the Shift Cores tab.
• Select the SHIFT core (at the receiving end of the white arrow) of the ties to be removed.
• Click the Break TIE button underneath the Shift table.
It is then your task to fix whatever consequences your action has. Correlator assists you by coloring the broken-out cores orange, representative of the status type REL.
4.3. Shift cores with the SET method
Rationale for using SET
Sometimes you may want to shift one or more cores by a certain distance or a certain percentage, rather than by tying them. Example use cases are:
• Seed core offsets: You know what the approximate growth rate will be (typically 1.05 to 1.1, or ~5 to 10% in APC cores) and you like to “seed” corresponding offsets for all cores so they are spaced out near their CCSF depth positions and are easier to tie together. This is particularly useful when you get data for a third or fourth hole after you have constructed a preliminary CCSF scale with the previous two or three holes, respectively.
• Adjust for an odd stratigraphic feature or coring artifact: A stratigraphic feature such as bedform or mass wasting may be inferred in a hole based on apparent increase or decrease in strata thickness. In some rare cases, an interval may have been cored twice (or been missed) by accident due to human or mechanical error. These situations can be mitigated by shifting cores by a fixed amount. On the SET dialog in Fig. 3-31, use the appropriate selections and apply.
• Extend the CCSF construct when ties are not possible: At some point, tying cores by correlating stratigraphic features in the data is not possible because of insufficient signal in the data or insufficient core coverage. This can be an intermittent interval where ties are possible above and below, or it occurs typically at greater depth. It is often possible to “stretch” the extent of the CCSF construct by applying a well-informed growth rate as a SET Percentage for one or more cores.
• You may have constructed a chain of tied cores and then decide that the seafloor reference (of the anchor core), or the position of a second chain at depth, should be changed by a small amount. Rather than having to start over building the entire chain, you can shift an entire chain of tied cores by a fixed distance.
SET options
To set one or more cores:
• Click the SET... button on the Shift Cores tab (Fig. 3-31).
• Select the Hole and a Core from the dropdown lists.
• Select one of three options for the scope of the shift (Fig. 3-31):
¿ Selected core and all untied cores below in this hole
¿ Selected core only
¿ Entire TIE chain starting from core… (select from available root cores)
• Opt whether to shift by:
¿ Percentage, a percentage of the original CSF-A depth, or
¿ Fixed distance (m), the absolute distance from the original depth CSF-A depth
• Add a comment for future users or yourself (optional)
• Click Cancel or Apply.
The following happens when you apply a shift with the SET method:
• The core trace is changed to blue to indicate the data has been depth adjusted by SET (Fig. 3-32).
• The type (SET) and amount of shift (m) is shown on the plot.
• The Shifts table is updated with the Type of one or more shifted cores changed to SET.
• The Growth Rate plot is updated.
Note: With the first two of the three SET scope options, cores that are in a TIE relationship cannot be SET. They first need to be un-tied (Fig. 3-33).
Note: The percentage or absolute shifts are always relative to the original CSF-A depth, not relative to the depth cores may already have been shifted! For example, a core may already have a cumulative offset of 5 m and if an absolute shift of 1 m is applied the core actually shifts 4 m upward, not 1 m downward.
Figure 3-31. Seeding core positions near their future CCSF depth. This needs to be done for each hole separately. Shown here is the SET dialog and the Shifts table, where all offsets are zero (and core traces are accordingly yellow).
Figure 3-32. All cores in Hole A are shifted by 5% of their CSF-A depth and are spaced out suitably for creating ties. The color of the core traces turned blue. The SET operation in this case would be repeated for holes B and D.
Figure 3-33. The attempt to SET cores that are part of a chain failed.
4.4. Undo shifts
You can undo shifts in two principal ways: one shift at a time, or all shifts in one swoop.
To undo shifts one at the time:
• Use the Undo Previous Shift button on the Shift Cores tab.
¿ Shifts that were achieved with the TIE and/or the SET methods are undone in the reverse order they were made.
¿ Undo also works for shifts that were saved to the affine table. Save/Update of the affine will account for any undo actions. (See below for more information on Save.)
Undo all shifts in one action by disabling the affine table:
• Go to the Data Manager (and save the affine table when prompted).
• Open the Saved Tables tree.
• Disable the affine (and splice, if applicable) table using the right-click context menu.
• If you try to switch directly back to display, you get the prompt in Fig. 3-41).
¿ Say No and you will not proceed to the Display, allowing you to Load the changes you made in the Data Manager, which will get you back to the Display with all shifts and ties gone.
¿ If you say Yes you will find the Display NOT representing the disable/enable action you just took.
• Disabling affine tables allows you to start over with all cores at the original CSF-A depths, while keeping the disabled affine table just in case you want to apply it again later.
Figure 3-41. Prompt when user tries to switch to Display without first re-loading the data.
Undo shifts in one action by deleting the affine table:
• Go to the Data Manager (and save the affine table when prompted)
• Open the Saved Tables tree.
• Delete an affine (and splice, if applicable) table using right-click context menu.
• You will get the warning in Fig. 3-42.
¿ Say OK and the table is gone, as intended. All you need to do now is select Load from the site folder and you are back to the Display, with all shifts undone.
¿ Say Cancel and nothing happens.
Figure 3-42. Deleting a table will clear the data from the Display. You need to Load the data again to ensure the Display reflects changes made in the Data manager.
4.5. Manage affine tables
Save affine table
Depth shifts are saved in an affine table within the Correlator application. Users can save as many affine tables as they like. Users have three ways to trigger a save of recent shift changes to the affine table, each:
• Click Go to Data Manager on the Tool Bar.
¿ The prompt in Fig. 3-51 appears.
¿ If you click Yes, the Save dialog in Fig. 3-52 comes up.
• Click Save on the Tool Bar, which brings up the Save dialog in Fig. 3-52.
• Click the Save Affine Table button on the Shift Cores tab, which also brings up the Save dialog in Fig. 3-52.
Figure 3-51. Save confirmation prompt.
Figure 3-52. Affine Save dialogue if the Save Affine Table button is used.
If no enabled affine table exists, the current shifts will be saved in a new, enabled affine table without any prompt or confirmation. The file name generated by Correlator will include a number that is incremented by 1 from the highest numbered affine in Correlator, including disabled affines.
If an enabled affine table exists, you have the option of updating an affine rather than creating a new one.
Upon saving, you will receive a confirmation (Fig. 3-53).
Figure 3-53. Confirmation message of successful affine table saving.
Enable and load affine table
If you want to use an affine table that already exist in Correlator but is disabled:
• Click Go to Data Manager on the Tool Bar and open the saved tables tree (Fig. 3-54).
• Enable the one you want to load – this will automatically disable the previously enabled one.
• Right-click on the saved tables item and choose Load from the context menu.
Figure 3-54. Saved affine tables are listed in the Data Manager. Only one can be enabled at any one time. Enabling a disabled one will disable the enabled one.
Export and Import affine table
To export your final affine table (i.e., to load it into the LIMS database), use the Export option on the context menu (Fig. 3-54).
In some cases, you may want to import an affine table that you exported in a previous session. To do so, right-click on the Saved Tables item in the Data Manager and select Import affine table. (Fig. 3-55).
Note the option to Import legacy affine table, which allows the import of affine tables created prior to Correlator v. 3.0.
Figure 3-55. Import an affine table function.
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5. Construct the splice
5.1. Splice concepts
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